To differentiate between studies with higher and lower risk of bias, we critically appraised all included validation studies according to check lists: Studies comparing two or more case definitions directly (ie, model A or B) were appraised according to the QUADAS criteria 28 (patient selection, index test, reference standard, flow and timing).
Moreover, it could be shown that a "significant difference in effect sizes […} between studies with a high or unclear risk of bias and those with a low risk of bias" exists [ 18].
Not only study design but also the evaluation of the risk of bias of individual studies showed relationships between studies with a higher risk of bias and positive (beneficial) results observed after PRP interventions, with 67.8% (19/28) [ 19, 21- 25, 26, 28, 29, 29, 34, 38, 39, 41, 55, 58, 69, 72- 74, 76] of high-risk studies having positive outcomes.
To ensure that the number of studies showing CBX2 upregulation was higher than those with CBX2 downregulation across all three time points, we performed a chi-square test and found a statistically significant difference between the studies with high and low CBX2 (P<0.00001, chi-square).
There were no significant differences in diagnostic accuracy between studies with low and high prior probability of disease in the patient sample.
If high quality trials could be found, comparisons between all of the studies and studies with high quality would be conducted.
But although they noticed demographic differences between study participants with high and low educational attainment and between high and low earners, the study wasn't sufficiently powered to examine those differences in a meaningful way.
The incidence of perineal trauma varies markedly between studies with occurrence tending to be higher in hospital settings compared with community settings [ 4].
The magnitude of the immune response was different between the 2 studies, with higher seroconversion and seroprotection rates found in Mali vs Ghana.
